Measurement of polarization observables T, P, and H in π0 and η photoproduction off quasi-free nucleons.

The target asymmetry T, recoil asymmetry P, and beam-target double polarization observable H were determined in exclusive π0 and η photoproduction off quasi-free protons and, for the first time, off quasi-free neutrons. The experiment was performed at the electron stretcher accelerator ELSA in Bonn, Germany, with the Crystal Barrel/TAPS detector setup, using a linearly polarized photon beam and a transversely polarized deuterated butanol target. Effects from the Fermi motion of the nucleons within deuterium were removed by a full kinematic reconstruction of the final state invariant mass. A comparison of the data obtained on the proton and on the neutron provides new insight into the isospin structure of the electromagnetic excitation of the nucleon. Earlier measurements of polarization observables in the γp→π0p and γp→ηp reactions are confirmed. The data obtained on the neutron are of particular relevance for clarifying the origin of the narrow structure in the ηn system at W=1.68GeV. A comparison with recent partial wave analyses favors the interpretation of this structure as arising from interference of the S11(1535) and S11(1650) resonances within the S11-partial wave.

Measurement of the helicity asymmetry E for the reaction γ p → π 0 p : The CBELSA/TAPS Collaboration.

A measurement of the double-polarization observable E for the reaction γ p → π 0 p is reported. The data were taken with the CBELSA/TAPS experiment at the ELSA facility in Bonn using the Bonn frozen-spin butanol (C 4 H 9 OH) target, which provided longitudinally-polarized protons. Circularly-polarized photons were produced via bremsstrahlung of longitudinally-polarized electrons. The data cover the photon energy range from E γ = 600 to 2310 MeV and nearly the complete angular range. The results are compared to and have been included in recent partial wave analyses.

Observation of the pη

Data on the beam asymmetry Σ in the photoproduction of η mesons off protons are reported for tagged photon energies from 1130 to 1790 MeV (mass range from W=1748 MeV to W=2045 MeV). The data cover the full solid angle that allows for a precise moment analysis. For the first time, a strong cusp effect in a polarization observable has been observed that is an effect of a branch-point singularity at the pη^{'} threshold [E_{γ}=1447 MeV (W=1896 MeV)]. The latest BnGa partial wave analysis includes the new beam asymmetry data and yields a strong indication for the N(1895)1/2^{-} nucleon resonance, demonstrating the importance of including all singularities for a correct determination of partial waves and resonance parameters.

Mitotic Waves in Laticifers of Euphorbia marginata.

A successive pattern of nuclear divisions that result in mitotic waves has been observed within the coenocytic nonarticulated laticifers of embryos of Euphorbia marginata Pursh. These waves originate independently in the cotyledonary or hypocotyl portion of the laticifer and exhibit uni-or bidirectional movement at variable velocities. Individual nuclei or groups of neighoring nuclei in a laticifer were observed in a sequence of mitotic stages ranging from prophase to telophase; division activity varied with individual laticifers in an embryo. Two mitotic patterns were apparent in the embryo: a random pattern associated with various cells in the meristematic area, and a successive pattern restricted to the laticifer. A substance, synthesized by and restricted to the laticifer, may be associated with this mitotic pattern.

Early development of the secretory cavity of peltate glands in Humulus lupulus L. (Cannabaceae).

Early development of the secretory cavity of chemically fixed peltate glands in Humulus lupulus L. showed secretions with different densities, light, gray and dark, in the cytoplasm of disc cells and in the periplasmic space adjacent to the developing secretory cavity. Secretions were detected in the disc cell wall and subsequently in the developing secretory cavity under the subcuticular wall of the sheath. Light and gray secretions in the cavity possessed a membrane-like surface feature. Secretions were in contact with the irregular inner surface of the cuticle. Secretions contributed to the thickening of the cuticle, whereas the membrane-like surface feature contributed to a network of Cannabis striae distributed throughout the cuticle. This study supports an early development and organization of the secretory cavity in H. lupulus, parallel to those in Cannabis, and may represent common features for lipophilic glands in angiosperms.

Plastid development in disc cells of glandular trichomes of Cannabis (Cannabaceae).

Plastids in lipophilic glandular trichomes of chemically fixed (CF) and high pressure cryofixed-cryosubstituted (HPC-CS) bracteal tissues of Cannabis were examined by transmission electron microscopy. In CF preparations, plastids in disc cells prior to secretory cavity formation possessed several lobed and dilated thylakoid-like features. In glands with secretory cavities, thylakoid-like features aggregated to form reticulate bodies that distended regions of the elongated plastids. Electron-gray inclusions evident on the plastid surface appeared continuous with the reticulate body. Inclusions of similar electron density also appeared in the cell cytoplasm, along the plasma membrane, between the plasma membrane and cell wall facing the cavity, and in the secretory cavity in both CF and HPC-CS preparations. The bilayer structure of membranes of the plastid envelope was evident in HPC-CS but not in CF preparations. In HPC-CS preparations, secretions were evident on the plastid surface and were continuous with those in the plastid through pores in the envelope. This study supports an interpretation that these specialized plastids, lipoplasts, synthesize secretions that are transported through the plasma membrane and cell wall to subsequently accumulate in the secretory cavity.

Vitreous fluorophotometry in pars planitis.

We used vitreous fluorophotometry to supplement standard clinical techniques and fluorescein angiography to study 23 eyes in 12 patients with pars planitis. All eyes leaked abnormal amounts of fluorescein into the vitreous. The leakage was generalized in the posterior segment of the eye. In milder cases, leakage was greater posteriorly; more severe cases showed preferential leakage from the equatorial and midperipheral regions. There was no predilection for leakage in the inferior fundus. The eyes in which greater leakage occurred inferiorly tended to be those with greater overall leakage; all but one involved early cyclitic membrane formation or heavy neovascularization of the pars plana membrane. The amount of cystoid macular edema demonstrated by fluorescein angiography correlated well with vitreous fluorophotometric values, as did vitreous haze, the extent and density of the inferior membrane, and visual acuity.

Scanning electron microscopy of starch grains from latex of Euphorbia terracina and E. tirucalli.

The morphology of starch grains isolated from the latex of 2 species of Euphorbia was compared by scanning electron microscopy. In E. terracina they are elongated and greater, in diameter at the midregion than at the tips while in E. tirucalli they are osteoid. Starch grains varied in size in both, species although in E. tirucalli the largest grains, which measured 49 µ, were approximately twice the length of those in E. terracina (27 µ).

Study of antibacterial activity and bacteriology of latex from Asclepias syriaca L.

Whole and fractionated latex of Asclepias syriaca was tested for antimicrobial or growth-promoting activity with 16 genera and species of bacteria. Latex and extracted fractions (distilled water, acetic acid, sodium bicarbonate, sulfuric acid, and ethyl ether) possessed no detectable antimicrobial activity. Comparison of growth curves of selected bacteria incubated with serum and rubber fractions, as well as controls, revealed no detectable inhibition of growth, except for a slight inhibitory response to autoclaved serum. Most bacteria were capable of utilizing latex for a substrate as indicated by the increased growth rate in the exponential phase. The stationary phase was entered simultaneously by both the treated cultures and the controls. Various bacteria cultured in a litmus latex mixture yielded populations which ranged from <10(4) organisms/ml for Lactobacillus casei, Staphylococcus aureus and Micrococcus lysodeikticus to 1.1 x 10(10) organisms/ml for Clostridium acetobutylicum. Whole latex, as well as the serum and rubber fractions, support the growth of various bacteria, but under field conditions there is no evidence for systemic infection of this type of cell by bacteria.

Immunochemical localization of tetrahydrocannabinol (THC) in cryofixed glandular trichomes of Cannabis (Cannabaceae).

Delta 9-tetrahydrocannabinol (THC) localization in glandular trichomes and bracteal tissues of Cannabis, prepared by high pressure cryofixation-cryosubstitution, was examined with a monoclonal antibody-colloidal gold probe by electron microscopy (EM). The antibody detected THC in the outer wall of disc cells during the presecretory cavity phase of gland development. Upon formation of the secretory cavity, the immunolabel detected THC in the disc cell wall facing the cavity as well as the subcuticular wall and cuticle throughout development of the secretory cavity. THC was detected in the fibrillar matrix associated with the disc cell and with this matrix in the secretory cavity. The antibody identified THC on the surface of secretory vesicles, but not in the secretory vesicles. Gold label also was localized in the anticlinal walls between adjacent disc cells and in the wall of dermal and mesophyll cells of the bract. Grains were absent or detected only occasionally in the cytoplasm of disc or other cells of the bract. No THC was detected in controls. These results indicate THC to be a natural product secreted particularly from disc cells and accumulated in the cell wall, the fibrillar matrix and surface feature of vesicles in the secretory cavity, the subcuticular wall, and the cuticle of glandular trichomes. THC, among other chemicals, accumulated in the cuticle may serve as a plant recognition signal to other organisms in the environment.

Accumulation of non-utilizable starch in laticifers of Euphorbia heterophylla and E. myrsinites.

Starch biosynthesis and degradation was studied in seedlings and mature plants of Euphorbia heterophylla L. and E. myrsinites L. Mature embryos, which lack starch grains in the non-articulated laticifers, develop into seedlings that accumulate starch rapidly when grown either in the light or the dark. Starch accumulation in laticifers of dark-grown seedlings was ca. 47 and 43% of total starch in light-grown controls in E. heterophylla and E. myrsinites, respectively. In light-grown seedlings, starch was present in laticifers as well as parenchyma of stems and leaves, whereas in dark-grown seedlings starch synthesis was almost exclusively limited to laticifers. In 7-month-old plants placed into total darkness, the starch in chyma was depleted within 6 d, whereas starch in laticifers was not mobilized. The starch content of latex in plants during development of floral primordia, flowering, and subsequent fruit formation remained rather constant. The results indicate that laticifers in seedlings divert embryonal storage reserves to synthesize starch even under stress conditions (darkness) in contrast to other cells, and that starch accumulated in laticifers does not serve as a metabolic reserve. The laticifer in Euphorbia functions in the accumulation and storage of secondary metabolites yet retains the capacity to produce, but not utilize starch, a primary metabolite.

Laticifers in stamens of Papaver somniferum L.

Articulated anastomosing laticifers were identified at both light and electron microscopic levels in the stamens of Papaver somniferum L. They were observed associated with the phloem forming a continuous system from the filament into the anther of the stamen. Laticifers, which were comparable in structure to laticifers found elsewhere in the plant, possessed numerous vesicles of different sizes within the protoplast.

Dopamine biosynthesis at different stages of plant development in Papaver somniferum.

Latex and cell-free extracts of various organs and stages of plant and capsule development in Papaver somniferum, the opium poppy, synthesized dopamine, an alkaloid precursor, from 14C-dopa. The 1000 g X 30 min supernatant from latex of the pedicel-capsule junction converted more dopa than latex supernatant from the upper capsule or lower pedicel regions, although there was more protein in the latex from the capsule. Percent conversion of pedicel-capsule latex into dopamine was maximum in unopened flower buds and decreased within 14 days after flowering. Dopamine biosynthesis in latex and cell-free extracts also varied with the stage of organ development. Extracts from capsule tissue converted more labeled dopa into dopamine than did extracts from pedicels, leaves from vegetative plants at the rosette stage, leaves from flowering plants, or pedicels connected to capsules.

Interrelationships of glandular trichomes and cannabinoid content. II. Developing vegetative leaves of Cannabis sativa L. (Cannabaceae).

Gland number and cannabinoid content were quantified during ontogeny of vegetative leaves from three clones of Cannabis. Initiation of capitatesessile and bulbous glands was found to occur uniformly during leaf development. Cannabinoids were synthesized throughout leaf development as well, but at a decreasing rate. A positive correlation was found for total capitate-sessile glands per leaf as compared with total cannabinoid content of the leaf. The data also indicated that other leaf tissues in addition to the glands may contain cannabinoids.

Interrelationships of glandular trichomes and cannabinoid content. I: Developing pistillate bracts of Cannabis sativa L. (Cannabaceae).

Gland number and cannabinoid content for three clones of Cannabis were compared. Cannabinoid levels and mature glands were quantified throughout progressive stages of pistillate bract development in order to define possible interrelationships between glands and cannabinoids. Similar trends occurred among the clones for each gland type while individual cannabinoids displayed a different pattern in each clone. Gland initiation and development as well as cannabinoid synthesis were found to occur during bract ontogeny for all three clones. A positive correlation existed for the total number of capitate glands per bract compared to the total cannabinoid content of the bract. The study also suggested that the glands may contain the majority of the cannabinoids present in the bract.